Memory devices and systems including multi-speed access of memory modules

ABSTRACT

A system, comprising: a plurality of modules, each module comprising a plurality of integrated circuits devices coupled to a module bus and a channel interface that communicates with a memory controller, at least a first module having a portion of its total module address space composed of first type memory cells having a first maximum access speed, and at least a second module having a portion of its total module address space composed of second type memory cells having a second maximum access speed slower than the first access speed.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/220,177, filed on Jun. 24, 2009, Ser. No.61/218,286 filed on Jun. 18, 2009, and Ser. No. 61/248,723 filed on Oct.5, 2009, the contents of all of which are incorporated by referenceherein.

This application is also a continuation-in-part of U.S. patentapplication Ser. No. 12/577,695, filed on Oct. 12, 2009, which claimsthe benefit of the following U.S. Provisional Patent Application Ser.No. 61/147,046 filed on Jan. 23, 2009, Ser. No. 61/158,680 filed on Mar.9, 2009, Ser. No. 61/167,856 filed on Apr. 8, 2009, and Ser. No.61/167,969 filed on Apr. 9, 2009.

TECHNICAL FIELD

The present disclosure relates generally to memory devices, and moreparticularly to a memory modules and circuits related to such modules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block schematic diagram of a system according to anembodiment.

FIG. 2 is a block schematic diagram of a chunk buffer module accordingto an embodiment.

FIG. 3 is a block schematic diagram of a memory space mapping in a chunkbuffer module according to an embodiment.

FIG. 4 is a timing diagram showing examples of accesses that may occurin a chunk buffer module according to an embodiment.

FIG. 5 is a timing diagram showing examples of accesses that may occurin a chunk buffer module according to another embodiment.

FIG. 6 is a block schematic diagram of a chunk buffer module accordingto a further embodiment.

FIG. 7 is a block schematic diagram of a rapid channel module accordingto an embodiment.

FIG. 8 is a block schematic diagram of a system according to anembodiment that includes rapid channel modules.

FIG. 9 is a timing diagram showing examples of accesses that may occurin a system having a rapid channel module according to an embodiment.

FIG. 10 is a block schematic diagram of a rapid channel module accordingto another embodiment.

FIG. 11 is a block schematic diagram of a stacked cache device memorymodule according to an embodiment.

FIG. 12 is a block schematic diagram of a stacked cache memory packagethat may be included in a stacked cache device memory module accordingto an embodiment. FIGS. 12A and 12B are side cross sectional views ofstacked cache memory devices according to embodiments.

FIG. 13 is a block schematic diagram of a cache device according to anembodiment.

FIG. 14 is a block schematic diagram of a cache device according toanother embodiment.

FIGS. 15A to 15C are block schematic diagrams showing pre-fetch on hitoperations that may occur in a stacked cache memory package according toan embodiment.

FIGS. 16A to 16C are block schematic diagrams showing pre-fetch on missoperations that may occur in a stacked cache memory package according toan embodiment.

FIG. 17 is a block schematic diagram of a system according to anotherembodiment.

FIGS. 18A to 18C are block schematic diagrams of systems having memorycontrollers with variable speed access according to various embodiments.

FIG. 19 is a block schematic diagram of a cache architecture accordingto an embodiment.

FIG. 20 is a top plan view of a cache device according to an embodiment.

DETAILED DESCRIPTION

Various embodiments will now be described that show circuits, integratedcircuit devices (ICs), modules containing ICs, and systems includingmodules, as well as corresponding methods related to the operations ofsuch circuits, devices and systems. In the following description, likesections are referred to by the same reference character but with thefirst digit(s) corresponding to the figure number.

Referring to FIG. 1, a system according to an embodiment is shown in ablock schematic diagram and designated by the general referencecharacter 100. A system 100 may include a number of memory modules102-00 to 102-31, each having storage locations accessible by signalsfrom a memory controller 104. Memory modules (102-00 to 102-31) mayprovide accesses to storage locations at more than one speed. Inparticular embodiments, for some accesses, a minimum read latency (timebetween application of a read command and the output of read data) maybe smaller than other types of accesses. Similarly, a minimum writelatency (time between application of write command and application ofwrite data) may vary between accesses. Such differences may be expressedin clock cycles, in the case of synchronously accessed modules, or maybe expressed at a time value, in the case of asynchronously orsynchronously accessed modules.

Further, in some embodiments, accesses along channels (106-0 to 106-3)may vary in frequency and/or voltage amplitude.

In the embodiment of FIG. 1, a memory controller 104 may access memorymodules (102-00 to 102-31) along a number of channels CH0-3 (106-0 to106-3). In particular, channel CH0 may access modules 102-00 and -01,channel CH1 may access modules 102-10 and -11, channel CH2 may accessmodules 102-20 and -21, and channel CH3 may access modules 102-30 and-31.

Variable speed access to modules may differ between embodiments. Forexample, in some embodiments, accesses along one or more channels may befaster or slower according to which portion of an address space isaccessed. That is, a “chunk” of total address space may be buffered forhigh speed access.

In other embodiments, accesses may be faster along one or more channelsin the event a storage location has been cached. That is, one or morecache devices may be present on a module to provide fast access tocached addresses. In contrast, non-cached addresses may be accessed at astandard speed (i.e., relatively slower with respect to a fast access).Still further, in such cached arrangements, cache devices may alsoenable dynamic scaling of data signal transfer characteristics,including but not limited to frequency and/or voltage scaling. That is,frequencies of data transfers and/or voltage amplitudes of data signalsalong a channel may be varied in cached system.

In still other embodiments, one channel may only provide access arelatively fast speed, while other channels may provide mixed speeds oronly a standard (relatively slower) access speed. That is, one channelmay include modules that are “rapid access channel” modules, havingmemory devices constructed of high speed memory devices.

Referring still to FIG. 1, in very particular embodiments, any of memorymodules 102-0- to -31 may include a number of integrated circuit devicesmounted on a module circuit board in an in-line fashion. Such a modulecircuit board may include board connections formed on at least one sideof the circuit board to provide a signal connection to a channel (any of106-0 to -3). In an embodiment like that of FIG. 1, a memory module maybe an in-line memory module (IMM), such as a single IMM (SIMM), or adual IMM (DIMM) in the event connections and memory circuits are formedon both sides of a module circuit board.

In this way, a system may include memory modules that provide variableaccess speeds to storage locations therein.

Referring to FIG. 2, a memory module according to one embodiment isshown in a block schematic diagram and designated by the generalreference character 202. Memory module 202 may include a buffer section208 and a number of standard speed memory integrated circuit (IC)devices 210-0 to -8 formed on a module circuit board 212.

In one particular embodiment, a memory module 202 may be one example ofany of those shown as 102-00 to -31 in FIG. 1.

Standard speed memory IC devices 210-0 to -8 may provide access to datastorage locations at a standard speed. In the embodiment shown, standardspeed memory IC devices (210-0 to -8) may be commonly connected to amodule bus 220. A module bus 220 may include address, command and datasignal lines for accessing standard speed memory IC devices (210-0 to-8).

A buffer section 208 may include a module interface 214, a high speedmemory section 216, and a signal generator circuit 218. A buffer section208 may provide access to storage locations at a faster speed thanstandard speed memory IC devices (210-0 to -8). A module interface 214may include signal connections for communication with a memorycontroller on a communication channel 206. For example, a moduleinterface 214 may include address connections for receiving addressdata, control connections for receiving control data (command and/ortiming), and data connections for transferring data between moduleinterface 214 and a memory controller (not shown in FIG. 2). A moduleinterface 214 may provide address, control, and data signal paths toboth a high speed memory section 216 as well as signal generator circuit218.

A high speed memory section 216 may include one or more high speedmemory IC devices. Such high speed memory IC devices may provide afaster access speed than standard memory IC devices 210-0 to -8. A highspeed memory section 216 may receive memory access requests from moduleinterface 214, and receive write data and output read data throughmodule interface 214.

A signal generator circuit 218 may be connected to module interface 214either directly, or through high speed memory section 216. A signalgenerator circuit 218 may drive signals on module bus 220 to accessstandard speed memory IC device 210-0 to -8. In addition, signalgenerator circuit 218 ma provide data on module bus 220 to moduleinterface 214.

In a particular embodiment, standard speed memory IC devices 210-0 to -8may be dynamic random access memory (DRAM) ICs, while a high speedmemory section 216 may include one or more static random access memory(SRAM) ICs. Such SRAM ICs may have faster access speeds than the DRAMICs. Thus, accesses to buffer section 208 may be faster than accesses tostandard speed memory IC devices 210-0 to -8.

Further, in one embodiment, standard speed memory IC devices 210-0 to -8may be DRAM ICs having a particular DRAM interface. A module interface214 may be a same interface as DRAM interfaces of such DRAM ICs, and asignal generator circuit 218 may repeat signals received at moduleinterface 214. In a particular embodiment, a DRAM interface may bedouble data rate (DDR) type interface. A high speed memory section 216may include SRAM ICs having interfaces compatible with the DRAMinterface, or may include circuits that convert DRAM interface signalsto signals compatible with a different SRAM interface.

In this way, a memory module may include a number of memory IC deviceshaving standard speed access, and one or more high speed memory deviceshaving access speeds faster than the standard speed devices.

Referring to FIG. 3, a module memory space mapping according to anembodiment is shown in a block diagram. In one embodiment, the memorymapping shown in FIG. 3 may be one example of memory mapping that mayinclude in a module like that of FIG. 2.

FIG. 3 shows module memory devices 322 and how a corresponding modulememory space 324 may be accessed. Module memory devices 322 show memoryIC devices included on a module having data storage locations accessibleby another device (e.g., memory controller). In the embodiment shown,module memory devices 322 may include standard speed memory IC devices310-0 to 310-x and a high speed memory IC device 326. Alternateembodiments, may include more than one high speed memory IC device.

A module memory space 324 shows an organization of storage locationsprovided by a module. As shown, a memory space 324 may be divided intotwo memory space portions 324-0 and 324-1. A first memory space portion324-0 may physically correspond to storage locations within standardspeed memory IC devices (310-0 to 310-x), while a second memory spaceportion 324-1 may physically correspond to storage locations within highspeed memory IC device 326. In the embodiment shown, first and secondmemory space portions 324-0 and -1 are not overlapping. That is,addresses applied to a module that access a first memory space portion324-0 are not the same as those that access second memory space portion324-1. Thus, a second memory space portion 324-1 may be conceptualizedas buffering a “chunk” of the total storage available on a module.

In a very particular embodiment, a module memory space 324 may bedividable into a number of memory lines 326-0 to 326-m, each including anumber of bytes (M). N bytes of each line (where N<M) may be stored byhigh speed memory IC device 326.

In one embodiment, standard speed memory IC devices may be DRAMs, whilea high speed memory IC device may be an SRAM.

In this way, a module may have a memory space with a portioncorresponding to standard speed memory IC devices and another, differentportion corresponding to high speed memory IC devices.

Referring to FIG. 4, a timing diagram shows an access operationaccording to an embodiment. FIG. 4 shows how variable speed accesses mayoccur over a same channel. Accesses shown by FIG. 4 may be particularexamples of memory accesses to a memory module like that shown as 202 inFIG. 2. The timing diagram of FIG. 4 shows a waveform for: command andaddress data (CMD/ADD) applied to a memory module, data applied oroutput corresponding to high speed memory devices (HIGH SPEED), and dataapplied or output corresponding to standard speed memory devices (STDSPEED).

Referring still to FIG. 4, at about time t0, a memory module may receivea command (e.g., read or write) and all, or a portion of an addresswithin the address space of a memory module.

In the event a command/address corresponds to a location within a highspeed memory device(s), corresponding data may be output (or input) at atime t1. In FIG. 4, the resulting delay is shown as Lat_HI.

In contrast, in the event a command/address corresponds to a locationwithin a standard speed memory device(s), data for the access may beoutput (or input) at a time t3, later than time t2. In FIG. 4, theresulting delay is shown as Lat_STD.

In the particular example shown, high speed accesses (i.e., data valuesD0-D3) and standard speed data accesses (i.e., data values D4-D7) mayoccur on a same communication channel (IMM CHANNELx).

In one very particular embodiment, data values may be output or input inbursts (e.g., data values may be input/output sequentially). Inaddition, a burst of data may occur over a time period “tburst” (in theexample shown, a burst of four). If a high speed latency and burst timeperiod are greater than or equal to a standard latency(Lat_HI+tburst≧Lat_STD), a single large burst (D0 to D7) may occur in anuninterrupted fashion that sequentially accesses both fast and standardspeed memory devices on a same channel. Such an operation may “hide” alonger latency (Lat_STD) by accessing high speed memory until a standardspeed memory access time has passed.

In this way, high and standard speed accesses may be combined to hide astandard latency for particular accesses.

Referring to FIG. 5, another timing diagram shows an access operationaccording to an embodiment. FIG. 5 shows how variable speed accesses mayoccur over a same channel in a memory module that includes SRAM devicesas high speed devices and DRAM devices as standard speed devices.Further, such a module operates according to synchronous DRAM accesscommands. Accesses shown by FIG. 5 may be particular examples of memoryaccesses to a memory module like that shown as 202 in FIG. 2.

The timing diagram of FIG. 5 shows a waveform for: command data (CMD),address data (ADD), and data output or applied along a module channel(i.e., read or write data) (DATA).

Referring still to FIG. 5, at about time t0, a memory module may receivean activation command (ACTV) along with a row address (ROW). Within DRAMdevices on a module, such a command may open a row. In one embodiment,for SRAM devices, such a row address may be stored for application withsubsequent address values.

At about time t1, a memory module may receive an access command (e.g., aread or write command) along with a column address (COL). Within DRAMdevices on the module, such a command may start to access storagelocations corresponding to the row and column address for availabilityafter a time TCL. In one embodiment, for SRAM device(s), such a columnaddress and command may be applied (along with the previous row address)to access storage locations within SRAM device(s).

At about time t2, after a time TaccSRAM, storage locations may beaccessible within SRAM device(s). Consequently, a first portion of adata burst (D0-D3) may be output or input at this time for locationswithin an SRAM device(s).

At about time t3, after a time TCL, storage locations may be accessiblewithin DRAM device(s). Consequently, a second portion of a data burst(D4-D7) may be output or input at this time for locations within DRAMdevices. It is noted that an SRAM data access time TaccSRAM and the timefor a corresponding data burst (t2 to t3), may be less than or equal toTCL.

In this way, SRAM device storage locations may be accessed while accessto DRAM storage locations is still in progress.

Referring now to FIG. 6, a chunk buffer memory module according to aparticular embodiment is shown in a block schematic diagram anddesignated by the general reference character 602. Chunk buffer module602 may be one particular example of that shown as 202 in FIG. 2.

Standard speed memory IC devices 610-0 to -8 may be double data rate(DDR) type synchronous DRAMs (SDRAMs), each of which may be connected toa module bus 620. A module bus 620 may include clock signal lines CLK,control signal lines (CTRL), address signal lines (ADD), bi-directionaldata lines (DQ), and data strobe lines (DQS). SDRAMs (610-0 to -8) mayhave interfaces compatible with module bus 620. SDRAMs may include DRAMtype memory cells that are periodically refreshed, and may processaddresses in a multiplexed fashion, receiving row addresses followed bycolumn addresses on a same set of address inputs. In addition, eachSDRAM (610-0 to -8) may be connected to only a portion of data lines DQ.As but one possible example, data lines DQ may be 72-bits wide, and eachof SDRAMs (610-0 to -8) may be connected to a different 8-bits of such a72-bit bus.

A buffer section 608 may include a module interface 614, a high speedmemory section 616, and a signal generator circuit 618. A moduleinterface 614 may correspond to interfaces of SDRAMs (610-0 to -8), andso may include module connections CLK_IN, CTRL_IN, ADD_IN, DQ_MOD andDQS_MOD corresponding to DQ, CTRL, ADD, DQ and DQS, respectively.Further, a signal generator circuit 618 may be buffer circuits that mayrepeat signals between module bus 620 and module interface 614, and thusisolate module bus 620 from module interface 614 in terms of loading.

In FIG. 6, a high speed memory section 616 may include one or more DDRsynchronous SRAMs (sync SRAMs) 626, an address processing circuit 628, adata strobe generation circuit 630, an optionally, a control/clockconversion circuit 632. Sync SRAMs 626 may include SRAM type memorycells that store data in a static fashion (e.g., are not periodicallyrefreshed). In the embodiment shown, sync SRAMs 626 may process addressvalues in parallel (e.g., address is not multiplexed), and may beconnected to only a portion of data lines DQ, but at a wider data widththan SDRAMs. As but one possible example, data lines DQ may be 72-bitswide, and there may be four sync SRAMs that are each connected to adifferent 18-bits of such 72-bits.

Address processing circuit 628 may receive address values received onmodule interface address inputs ADD_IN, and process such values togenerate applied address values to sync SRAMs 626. In one embodiment,such processing may include generating one address from two addressvalues (e.g., converting a row/column multiplexed address into a singleapplied address). In some embodiments, such processing may also includemanipulation of address values, including offsetting a received address,or other address translation operations. A data strobe generationcircuit 630 may generate a data strobe signal suitable for moduleinterface 614. In one embodiment, such a circuit may manipulate a phaseof clock signal CLK_IN to generate one or more data strobe signals.Optional control/clock conversion circuit 632 may convert DRAMcompatible control signals into sync SRAM compatible control signals, inthe event such command formats are different. In addition, control/clockconversion circuit 632 may alter clock signals CLK of module bus toprovide input clock signals to sync SRAMs 626, as needed.

In this way, a memory module may include sync SRAMs and SDRAMs, withsync SRAMs buffering a chunk of the total address space of the memorymodule.

Referring to FIG. 7, a rapid channel memory module according to anotherembodiment is shown in a block schematic diagram and designated by thegeneral reference character 702. Memory module 702 may include aninterface circuit 734 and a number of high-speed memory IC devices 736-0to -8 formed on a module circuit board 712. In one particularembodiment, a memory module 702 may be one example of any of those shownas 102-00 to -31 in FIG. 1.

High speed memory IC devices 736-0 to -8 may provide access to datastorage locations at a speed faster than other modules in a system. Inthe embodiment shown, high speed memory IC devices (736-0 to -8) may becommonly connected to a module bus 720. A module bus 720 may includeaddress, command and data signal lines compatible with high speed memoryIC devices (736-0 to -8).

In one embodiment, an interface circuit 734 may receive signals that arenot compatible with high speed memory IC devices (736-0 to -8), andconvert such signals for application to high speed memory IC devices(736-0 to -8). In a very particular embodiment, high speed memory ICdevices 736-0 to -8 may be SRAM ICs. Such SRAM ICs may have fasteraccess speeds than the DRAM ICs, which may serve as storage devices onother modules of a system.

In one embodiment, interface circuit 734 may be a particular DRAMinterface. In a particular embodiment, such a DRAM interface may be aDDR SDRAM type interface.

In this way, a memory module may include a number of memory IC deviceshaving high speed access.

Referring to FIG. 8, a system according to another embodiment is shownin a block schematic diagram and designated by the general referencecharacter 800. A system 800 may include both standard speed memorymodules 838-00 to -21 as well as rapid channel memory modules 840-00 to-01, each having storage locations accessible by signals from a memorycontroller 804.

In the embodiment shown, standard speed memory modules (838-00 to -21)may provide accesses to storage locations at a standard speed, whilerapid channel memory modules 840-00 to -01 may provide accesses tostorage location at a speed faster than that of standard speed memorymodules (838-00 to -21).

In FIG. 8, a memory controller 804 may access memory modules (838-00 to838-21, 840-00/01) along a number of channels CH0-3 (806-0 to 806-3).Channels CH0 to CH2 may be connected to standard speed memory modules838-00/01, -10/11, -20/21, respectively. Consequently, such channels(CH0-CH2) may be standard speed channels. In contrast, channel CH3 maybe connected to high speed memory modules 840-00/01, such as that shownin FIG. 7. Thus, channel CH3 may be considered a rapid channel. In suchan arrangement, a memory controller 804 may prioritize accesses, havingfast accesses available along channel CH3.

In this way, a system may include different speed memory modules ondifferent channels.

Referring to FIG. 9, a timing diagram shows an access operationaccording to an embodiment. FIG. 9 shows accesses that may occur overdifferent speed channels. Accesses shown by FIG. 9 may be particularexamples of memory accesses of a system like that shown as 800 in FIG.8. The timing diagram of FIG. 9 shows waveforms for a rapid channelRAPID CHANNEL (e.g., CH3 of FIG. 8), as well as waveforms for a standardchannel STD CHANNEL (e.g., CH0-2 of FIG. 8).

Referring still to FIG. 9, at about time t0, a memory module may receivea command (e.g., read or write) and all, or a portion of, an addresswithin the address space of a memory module.

As shown, on a rapid speed channel, a data access may begin at abouttime t1 after a delay of about Lat_HI. In contrast, on a standard speedchannel, a data access may begin at about time t2 after a delay of aboutLat_STD.

In this way, accesses may be made by a memory controller at differentspeeds on different channels.

Referring now to FIG. 10, a rapid channel memory module according to aparticular embodiment is shown in a block schematic diagram anddesignated by the general reference character 1002. Rapid channel memorymodule 1002 may be one particular example of that shown in FIG. 7, andthus include a module interface 1014 and high speed memory IC devices1036-0 to -8.

High speed memory IC devices (1036-0 to -8) may be DDR type sync SRAMs,each of which may be connected to a module bus 1020. A module bus 1020may include clock signal lines CLK, control signal lines (CTRL), addresssignal lines (ADD), bi-directional data lines (DQ), and data clock lines(K). In the embodiment shown, sync SRAMs (1036-0 to -8) may haveinterfaces that are not compatible with a module interface. Sync SRAMsmay include SRAM type memory cells that are not are periodicallyrefreshed. In addition, each sync SRAM (1036-0 to -8) may be connectedto only a portion of data lines DQ. As but one possible example, datalines DQ may be 72-bits wide, and each of SDRAMs (1010-0 to -8) may beconnected to a different 8-bits of such 72-bits.

A module interface 1014 may provide an interface for rapid channelmemory module 1002 that corresponds to interfaces of SDRAMs, and in theembodiment shown, may include module connections CLK_IN, CTRL_IN,ADD_IN, DQ_MOD and DQS_MOD. In FIG. 10, a module interface 1014 includesan address processing circuit 1028, a data strobe generation circuit1030, an optionally a control/clock conversion circuit 1032. Suchcircuits may operate as described for items 628, 630 and 632 of FIG. 6,respectively. That is, such circuits may convert SDRAM control signalsand data formats, to signals and formats compatible with sync SRAMs.

-   -   In this way, a memory module may include an SDRAM interface, but        store data with sync SRAMs.

Referring to FIG. 11, a stacked cache device memory module according toa further embodiment is shown in a block schematic diagram anddesignated by the general reference character 1102. Memory module 1102may include a number of stacked cache memory IC packages 1142-0 to -8connected to a module interface 1144 by a module bus 1120. In oneparticular embodiment, a memory module 1102 may be one example of any ofthose shown as 102-00 to -31 in FIG. 1.

Each stacked cache memory IC package 1142-0 to -8 may include one ormore cache memory ICs and one or more standard speed memory ICs. A cachememory IC may cache a portion of an address space stored by itscorresponding standard speed memory ICs. Accesses to addresses cached bya cache memory IC are faster than accesses to corresponding standardspeed memory ICs.

In this way, a memory module may include a number of memory IC packagesthat each includes one or more cache memory ICs and standard speedmemory ICs.

Referring to FIG. 12, a stacked cache memory IC package according to oneembodiment is shown in a block schematic diagram and designated by thegeneral reference character 1242. A package 1242 may include a packagecache device 1246 and standard memory ICs 1248-0 to -3. While FIG. 12shows one package cache device and four standard memory ICs, the numberof devices may vary in other embodiments.

A package cache device 1246 may include a cache memory 1250, a cachecontroller circuit 1252, a package interface 1254, controller interface1256, and memory control connections 1258. A cache memory 1250 mayinclude storage circuits for caching data from standard memory ICs(1248-0 to -3). Thus, a cache memory 1250 may be accessed in place of anaccess to standard memory ICs (1248-0 to -3).

A cache controller circuit 1252 may detect cache “hits”, and inresponse, control access to cache memory 1250. A cache hit may occurwhen access is requested for data stored in cache memory 1250 that waspreviously retrieved from standard memory ICs (1248-0 to -3). A cachememory 1250 may be based on a memory technology that provides fasteraccess than standard memory ICs (1248-0 to -3). In a very particularembodiment, cache memory 1250 may be based on SRAM cells, and standardmemory ICs (1248-0 to -3) may include DRAM cells to store data.

A controller interface (I/F) 1256 may receive address and commandsignals received on package interface 1254 (some shown as ADD/CTRL) andprovide such values for cache controller circuit 1252. In the particularembodiment shown, a controller I/F 1256 may also receive externallygenerated input data values, and output data values on controllerconnections (shown as data input/output connections (DQ)).

Memory control connections 1258 may provide signals for accessingstandard memory ICs (1248-0 to -3) within stacked cache memory ICpackage 1242. In the very particular embodiment of FIG. 12, memorycontrol connections 1258 include output connections for address andcontrol signals ADD/CTRL′, which may correspond to input signalsADD/CTRL at package connections 1254. In addition, memory controlconnections 1258 may include data I/Os DQ′. A stacked cache memory ICpackage 1242 may be a single integrated circuit package containingmultiple dice, electrically interconnected to one another.

Referring still to FIG. 12, a cache hit read operation according to anembodiment is shown. Address and control signals ADD/CTRL (shown by boldlines) may be received. It is assumed that an address corresponds todata already cached within cache memory 1250 resulting in a cache “hit”.That is, while data to be read is stored in one or more standard speedmemory ICs (1248-0 to 1248-3), the same data has been previously cachedwithin cache memory 1250. In response to the cache hit, cached datavalues (shown by bold lines) may be output on package connections 1254,in lieu of outputting data from standard speed memory ICs (1248-0 to1248-3). Data locations may be accessed from a cache memory 1250 atsubstantially faster speeds than locations within standard speed memoryICs (1248-0 to 1248-3).

Referring to FIG. 12A, a stacked cache memory IC package according to aparticular embodiment is shown in side cross sectional view anddesignated by the general reference character 1242′. A package 1242′ mayinclude standard speed memory ICs 1248-0′/1′ arranged horizontally witha package cache device 1246′. Access to such devices within package1242′ may be by way of package connections 1254′. A package 1242′ may beone implementation of that shown in FIG. 12.

Referring to FIG. 12B, a stacked cache memory IC package according toanother particular embodiment is shown in side cross sectional view anddesignated by the general reference character 1242″. A package 1242″ mayinclude standard speed memory devices 1248-0″/1″ arranged vertically apackage cache device 1246″. Access to such devices within package 1242′may be by way of package connections 1254′. A package 1242″ may be oneimplementation of that shown in FIG. 12.

In this way, a stacked cache memory IC package may include one or morepackage cache devices along with one or more standard speed memory ICs.Accesses to data cached data may be faster than non-cached data.

Referring to FIG. 13, a package cache device 1346 according to oneembodiment is shown in a block schematic diagram. A package cache device1346 may be one example of that shown as 1246, 1246′ or 1246″ in any ofFIG. 12, 12A or 12B. The package cache device 1346 may be one particularexample of a “look-side” type cache device.

A package cache device 1346 may include a cache memory 1350, a cachecontroller circuit 1352, a cache controller interface (I/F) 1356, and abus isolation circuit 1364. A cache memory 1350 may have storagelocations that cache data for other memory locations. A cache memory1350 may be controlled by a cache controller circuit 1352 to store dataand/or output data. A cache controller circuit 1352 may receive controlsignals from a cache controller I/F 1356, and in response, enable accessto cache memory 1350. Such accesses may have a predetermined timingrelationship with respect to received control signals. For example, inresponse to a control signals, data may be output or written into cachememory a predetermined time period (e.g., clock cycles) afterward.

A bus isolation circuit 1364 may control how signals are transmittedbetween package interface 1356 and standard speed memory ICs (not shown)within the same package. In a particular embodiment, a bus isolationcircuit 1364 may receive control signals and input data signals withoutincluding the load of standard speed memory ICs attached to memorycontrol connections 1366. For non-cache accesses, input signals receivedon controller interface 1356 may be repeated on memory controlconnections 1366, and similarly, output signals on memory controlconnections 1366 may be output on controller interface 1356.

In this way, a package cache device may be a look-aside cache devicehaving a bus isolation circuit for selectively isolating signalsreceived from a memory controller from signals output to control memorycircuits.

Referring to FIG. 14, a package cache device 1446 according to anotherembodiment is shown in a block schematic diagram. A package cache device1446 may be one example of that shown as 1246, 1246′ or 1246″ in any ofFIG. 12, 12A or 12B. The package cache device 1446 may be one particularexample of a “look-through” type cache device.

Referring to FIG. 14, a package cache device 1446 may include a cachememory 1450, a cache controller circuit 1452, a cache controller I/F1456, and a standard speed memory interface 1464. In such a look-througharchitecture, signals received by controller interface 1456 may bedecoded, and new control signals and/or data signals may be generated atstandard speed memory interface 1464.

In this way, a package cache memory device may have a look-througharchitecture.

Referring still to FIG. 14, in still other embodiments a look throughcache like that of FIG. 14 may be substituted for, or included as partof a high speed memory section 216. A cache controller 1452 may controlinterfaces 1456 and 1464 to provide dynamic frequency and/or voltagescaling. As but one example, accesses to a cache memory 1450 may occurat one frequency and/or according to one latency, while accesses througha cache 1446 to standard speed memory devices (e.g., 210-0 to 210-8) mayoccur at another frequency and/or according to another latency.

Referring now to FIGS. 15A to 15C, operations of a stacked cache memoryIC package according to an embodiment are shown in a series of blockdiagrams. The stacked cache memory IC may be one example of any of thoseshown as 1142-0 to -8 in FIG. 11. FIGS. 15A to 15C show one example of a“pre-fetch on hit” type of operation. In such an operation, in the eventof a read cache hit (e.g., read operation to data already cached in apackage cache device), cached read data may be output, and in addition,data from a different location is cached (i.e., is “pre-fetched”).Pre-fetching data in this fashion may increase the probability ofanother cache hit in a subsequent memory access.

A stacked cache memory IC package 1542 may include a package cachedevice 1546 and a number of standard speed memory ICs 1548-00 to1548-03. In the particular embodiments of FIGS. 15A to 15C, a packagecache device 1546 may have a particular look-aside architecture,however, alternate pre-fetch embodiments may include a package cachedevice having a different look aside architecture, or alternatively,having a look through architecture, like that shown in FIG. 14.

Referring still to FIGS. 15A to 15C, in the embodiments shown it isassumed that standard speed memory ICs (1548-00 to 1548-03) store firstdata “Dy” and second data “Dz” at separate addressable locations. It isalso assumed that data values Dy and Dz have a predeterminedrelationship conducive to pre-fetching. That is, if data Dy is accessed,it is likely that data Dz will be accessed. In some embodiments, such arelationship may be simply an adjacent address, but in otherembodiments, may be more complex, based on address range values, or somearithmetic/logic operation. It is also assumed that data Dy has beencached within package cache device 1542 by a previous operation.

Referring now to FIG. 15A, a stacked cache memory IC package 1542 mayreceive address and control values (shown by a bold line) that indicatea read request for data Dy at address ADDy (READ ADDy). Isolation buffer1566 may forward such a request for processing by circuits of packagecache device 1546. Optionally, such data may be forwarded to standardspeed memory ICs (1548-00 to 1548-03). In such a case, resulting readdata from standard speed memory ICs (1548-00 to 1548-03) may beprevented from being output by placing isolation circuit 1568 into ahigh impedance state, or by disabling standard speed memory ICs (1548-0to 1548-18) with control signals (e.g., clock enable signals (CKE))generated by package cache device 1546. Package cache device 1546 maycompare the received address to cached addresses. Because data value Dyis already stored, package cache device 1546 may detect a read cachehit.

Referring to FIG. 15B, in response to the read cache hit, package cachedevice 1542 may enable isolation buffer 1570 and output cached data(Dy[0:7]). In addition, package cache device 1542 may generate apre-fetch address and corresponding read control signals to pre-fetchdata Dz (PRE-FETCH READ ADDz). Such address/control values may be outputto standard speed memory ICs 1548-00 to 1548-03.

Referring to FIG. 15C, in response to the pre-fetch address and controlsignals (PRE-FETCH READ ADDz), standard speed memory ICs 1548-00 to1548-03 may output pre-fetched data (PRE-FETCH DATAz) which may bereceived by package cache device 1546 and stored as newly cached data.In the particular embodiment shown, package cache device 1546 may placeisolation buffer circuits 1570 and 1568 into high impedance states assuch cached data is stored.

In this way, a memory device may pre-fetch stored data in response to acache hit to increase the possibility of another cache hit in asubsequent operation.

Referring now to FIGS. 16A to 16C, operations of a stacked cache memoryIC package 1642 according to another embodiment are shown in a series ofblock diagrams. The stacked cache memory IC may be one example of any ofthose shown as 1142-0 to -8 in FIG. 11. FIGS. 16A to 16C show oneexample of a “pre-fetch on miss” type of operation. In such anoperation, in the event of a read cache miss (e.g., read operation todata not already cached in a module cache device), read data may beoutput and cached from standard speed devices, and in addition, datafrom a different location is cached (i.e., is “pre-fetched”).Pre-fetching data in this fashion may increase the probability ofanother cache hit in a subsequent memory access. A stacked cache memoryIC package 1642 may include some of the same sections as FIGS. 15A to15C, accordingly, like sections are referred to with the same referencecharacter but with the first digits being a “16” instead of “15”.

In the embodiments of FIGS. 16A to 16C, it is assumed that first data“Dy” is stored within standard speed memory circuits 1648-0 to -03.Further, as in the case of FIGS. 15A to 15C, data Dz is good pre-fetchcandidate with respect to data Dy. It is also assumed that neither dataDy nor data Dz has been cached within package cache device 1646.

Referring to FIG. 16A, a stacked cache memory IC package 1642 mayreceive address and control values (READ ADDy) that indicate a readrequest for data Dy at address ADDy. Further, such address and controlsignals are provided to package cache device 1646 by isolation buffer1666. However, unlike the embodiments of FIGS. 15A to 15C, a comparisonby package cache device 1646 indicates a cache miss. In response to sucha read cache miss, or regardless of such a miss, address and controlsignals (READ ADDy) may be applied to standard speed memory ICs (1648-0to -3).

Referring to FIG. 16B, in response to read address and control data,data READ Dy may be output from standard speed memory ICs (1648-00 to1648-03). Such read data (Dy[0:7]) may be output by isolation circuit1668. In addition, such read data (Dy[0:7]) may also be cached withinpackage cache device 1646. In response to the cache miss, a packagecache device 1646 may generate pre-fetch signals (PRE-FETCH READ ADDz)for pre-fetching data Dz within standard speed memory ICs (1648-0 to-3). It is noted that such pre-fetch signals may be generated prior to,coincident with, or after the output read data Dy[0:7].

Referring to FIG. 16C, in response to the pre-fetch address and controlsignals (PRE-FETCH READ ADDz), pre-fetched data 958 (PRE-FETCH Dz) maybe output from standard speed memory ICs (1648-0 to -3). In theparticular embodiment shown, package cache device 1646 may placeisolation buffer circuits 1670 and 1668 into high impedance states, andstore the cached data (Dz[0:7]).

In one embodiment, a package cache device 1646 may be a dual port devicethat may allow data to be received concurrently at two different dataports. In such an arrangement, read data (e.g., Dy[0:7]) may be outputand cached at the same time pre-fetch data (e.g., Dz[0:7]) is cached.

In this way, a package cache device may pre-fetch data stored instandard speed memory ICs of a same package in response to a cache miss.Such an action may increase the possibility of another cache hit in asubsequent access operation.

Referring to FIG. 17, a system according to another embodiment is shownin a block schematic diagram and designated by the general referencecharacter 1700. A system memory 1700 may be a computing system thatincludes a number of circuit board groups 1772-0 to 1772-2, eachconnected to a processing package 1776. Each circuit board group 1772-0to 1772-2 may include a number of circuit boards (one shown as 1712).Each circuit board (e.g., 1712) may include storage locations accessibleby variable access speeds according to embodiments shown herein, orequivalents.

A system 1700 may be one implementation of that shown as 100 in FIG. 1.

Circuit board groups 1772-0 to 1772-2 may collectively form a systemmemory 1774. Such a system memory 1774 may be increased in capacity byadding more circuit boards (e.g., 1712) or decreased in size by removingsuch circuit boards.

A processing package 1776 may access memory on circuit boards (e.g.,1712) with read and/or write operations. In response to such operations,circuit boards (e.g., 1712) may provide variable access speeds. That is,such circuit boards may services some requests at a faster speed (e.g.,lower latency) than other requests. The very particular processingpackage 1776 of FIG. 17 may be a multi-processor system includingmultiple central processing units (CPUs) (one shown as 1778), and threelayers of “on-board” cache (shown as L1, L2 and L3). An on-board cachemay be formed in a same substrate as an integrated circuit including aCPU and/or may be a memory integrated circuit included within amultichip module containing one or more CPUs.

Layer 1 cache (L1) may include both instruction and data caches,accessible by a corresponding CPU. Layer 2 cache (L2) may be a datacache also accessible by a corresponding CPU. Layer 3 (L3) cache may bea shared data cache accessible by any of the CPUs. It is noted thaton-board caches L1, L2 and L3 do not scale with changes in the size ofsystem memory 1774.

In sharp contrast, an amount of high speed memory may scale with a sizeof system memory 1774. For example, if a system memory 1774 includeschunk buffered modules, like that shown in FIG. 2, increasing the numberof such modules in a system memory 1774 increases the amount of totalmemory space buffered by high speed access devices. Further, if a systemmemory 1774 includes a rapid channel module, like that shown in FIG. 7,increasing the number of such modules in a system memory 1774 increasesthe amount of memory on a rapid channel. Still further, if a systemmemory 1774 includes stacked cache device memory modules, like thatshown in FIG. 11, increasing the number of such modules in a systemmemory 1774 increases the amount of memory cached, and therefore theamount of data available at a lower latency.

Referring still to FIG. 17, exemplary access speeds, noted in CPU clockcycle time units are shown. Accesses to layer 1 cache (L1) may occurwithin 3-4 clock cycles. Access to layer 2 cache (L2) may occur within10-15 clock cycles. Accesses to shared layer 3 cache (L3) may occur in35-50 clock cycles. Slower speed accesses may take from 150-200 clockcycles. However, faster speed accesses (e.g., accesses to bufferedmemory, rapid channel modules, or locations cached on modules) may be60-75 clock cycles, improving performance over a system memory thatincludes only standard speed devices (e.g., system memory ofconventional DIMMs).

In this way, a system may have a system memory with fast accesslocations that scale with the size of the system memory.

By including a variable speed modules as shown in the embodiments hereinand equivalents, access times for a memory controller may vary. FIGS.18A to 18C show various systems with memory controller that mayaccommodate variable accesses to a memory module.

Referring to FIG. 18A, a system according to an embodiment is shown in ablock diagram and designated by the general reference character 1800. Asystem 1800 may include one or more memory modules (one shown as 1802)that may be connected to a memory controller 1804. In the embodimentshown, a memory module 1802 may be a stacked cache device module, likethat shown in FIG. 11. A stacked cache device module 1802 may return apredetermined signal to a memory controller 1804 in the event of a cachehit.

A memory module 1802 may be attached to a memory controller 1804 bycontroller connections 1888-0 and 1888-1. Controller connections 1888-0may provide control and address signals, and in one particularembodiment, may be one-way connections from memory controller 1804 tomemory module 1802. In alternate embodiments, controller connections1888-0 may include a bi-directional path and/or a one-way signal pathfrom memory module 1802 to memory controller 1804 that may enable acache indication to be sent to the memory controller 1804. Controllerconnections 1888-1 may provide data values, and in one embodiment may bebi-directional, allowing read data to be output to memory controller1804 or write data to be input from memory controller 1804. In alternateembodiments, controller connections 1888-1 may include separate one-waysignal paths for read and write data.

A memory controller 1804 may include a data input circuit 1890, acontroller circuit 1892, and data driver circuits 1894. A data inputcircuit 1890 may allow data from memory module 1802 to flow through tocontroller circuit 1892. A data driver circuit 1894 may drive data forinput to memory module 1802. A controller circuit 1892 may monitor acache hit indication from memory module 1802, and in response, alter alatency at which read data is received (e.g., latched) and/or write datais driven by data driver circuit 1894. In the very particular embodimentof FIG. 18A, a memory controller 1804 may have storage locations for twoor more latency values to enable controller circuit 1892 to alteroperations based on detecting a cache hit or miss. FIG. 18 shows twoparticular values Latency MISS (LMiss) and Latency HIT (LHIT). However,such values may be “hardwired” into a circuit or inherent in a circuitresponse.

In this way, a memory module may provide a cache hit indication to amemory controller. In addition or alternatively, a memory controller mayrespond with different latencies depending upon a cache hit indicationfrom a memory module.

Referring to FIG. 18B, a system according to another embodiment is shownin a block diagram and designated by the general reference character1800′. A system 1800′ may include some sections like those of FIG. 18A.However, in FIG. 18B one or more memory modules (one shown as 1802′) mayinclude a chunk buffered module, like that shown in FIG. 2. A chunkbuffered module 1802′ may have a portion of an address space stored byhigh speed memory devices, while another portion of the address space isstored in standard speed memory devices.

A controller circuit 1892 may have range information (ADD_Range FAST)that identifies which addresses correspond to high speed memory devices.Such a range value may be programmable, or may be hard wired into thecircuit. Further, a memory controller 1804 may have storage locationsfor two or more latency values to enable controller circuit 1892 toalter operations based on accesses within range ADD_Range FAST, versusaccesses outside such a arrange. FIG. 18B shows two particular valuesLatency STD and Latency FAST. Such values may be hardwired into acircuit or inherent in a circuit response.

In this way, a memory controller may respond with different latenciesdepending upon the address accessed in an operation.

Referring to FIG. 18C, a system according to a further embodiment isshown in a block diagram and designated by the general referencecharacter 1800″. A system 1800″ may include some sections like those ofFIG. 18A. However, in FIG. 18C one or more memory modules (one shown as1802″) may include a rapid channel module, like that shown in FIG. 7. Arapid channel module 1802″ may be formed of high speed memory devices,as opposed to other modules of the system.

A controller circuit 1892 may have channel information (CHANNEL FAST)that identifies which channels include rapid channel modules. Further, amemory controller 1804 may have storage locations for two or morelatency values to enable controller circuit 1892 to alter operationsbased on accesses to different channels. FIG. 18C shows two particularvalues Latency STD and Latency FAST. Such values may be hardwired into acircuit or inherent in a circuit response.

In this way, a memory controller may respond with different latenciesdepending upon the channel accessed in an operation.

Referring now to FIG. 19, one example of a cache architecture that maybe included in embodiments is shown in a block schematic diagram anddesignated by the general reference character 1982. A cache architecture1982 may be included in a cache device. As but one example, a cachearchitecture may correspond to a package cache device, like that shownas 1246 in FIG. 12. However, such a cache architecture may be includedin various other implementations, including but not limited to aseparate IC on a memory module, or a separate IC between a memorycontroller and one or more memory modules.

A cache architecture 1982 may include a cache input 1984, tag blocks1986-0/1, a compare section 1996, a data block 1903, a cache data outputcontrol 1998, and hit logic 1901. A cache input 1984 may receive valuesTAG, SETV and OFFSET in response to received address data. In oneparticular embodiment, there may be a one-to-one bit correspondencebetween address data and the fields TAG, SETV and OFFSET. In analternate embodiment, address translation or some other operation maygenerate values TAG, SETV and OFFSET from a received address value.

While the embodiment of FIG. 19 shows two tag blocks (1986-0 and1986-1), a number of tag blocks may be configurable. Each tag block(1986-0 and 1986-1) may include a number of entries accessible by valuesSETV and optionally value OFFSET, and according to a particular accesscycle. Each entry within a tag block (1986-0 and 1986-1) may include acached tag value TAG′ and a USE value. A cached tag value TAG′ may beused for comparison with an input TAG value. A USE value may indicate anentry's validity (is the entry used or available) and/or may indicatethe last time an entry was used, or the number of times an entry hasbeen used. Such a USE value can be used to dictate when a cache entry isto be freed up (i.e., evicted) for use by a new cache value. If a SETVvalue corresponds to an entry within a tag block (1986-0 to 1986-1) acorresponding tag value TAG′ will be output to compare section 1996.

Values within tag blocks (1986-0 and 1986-1) may be logically arrangedinto sections accessed on different cycles. In the embodiment shown, tagblock 1986-0 has been arranged to include section 1905-0 c 1 accessibleon a first cycle, and section 1905-0 c 2 accessed on a subsequent cycle.Similarly, tag block 1986-1 has been arranged to include section 1905-1c 1 accessible on the first cycle, and section 1905-1 c 2 accessed on asubsequent cycle. The number of sections within a tag block may beconfigurable. In a very particular embodiment, an input tag values TAGand cached tag values TAG′ may be portions of a larger tag value.Accordingly, a valid cache hit may result when hits occur over multiplecycles.

Accordingly, a cache architecture 1982 may provide for configurableassociativity. That is, a set value may be configurable for a differentgranularity in cache compare tries. A cache input 1984 may receivevalues TAG, SETV and OFFSET.

A compare section 1996 may compare a cached values TAG′ to input valueTAG to thereby determine if a hit has occurred in any tag block(1986-0/1). In the very particular example of FIG. 19, a compare section1996 may include comparators 1907-0 and 1907-1, which may each comparean input tag value TAG to a cached tag value TAG′ output from tag blocks1986-0 to 1986-2 on a given cycle, to thereby generate a block hitindications A and B.

Cache hit logic 1901 may provide a HIT indication representing when astored tag value TAG′ matches an applied tag value. It is noted that ifa “hit” occurs on one cycle, searches for subsequent cycles may becancelled. This may save the amount of power consumed in cache matchoperations. In addition or alternatively, cache hit logic 1901 maylogically combine block hit indications A and B according to clockcycles (cycle 1 and cycle 2), in the event each stored tag value TAG′ isone portion of a larger value.

A data block 1903 may include a number of entries accessible by valueSETV and, optionally, value OFFSET. A data block 1903 may be organizedinto groups corresponding to both tag blocks and access cycles. In theparticular example of FIG. 19, data block 1903 may include group 1909-0,which may correspond to tag block 1986-0 and cycle 1, group 1909-1,which may correspond to tag block 1986-1 and cycle 1, group 1909-2,which may correspond to tag block 1986-0 and cycle 2, and group 1909-3,which may correspond to tag block 1986-1 and cycle 2.

A cache data output control 1998 may output cached data DATA from datablock 1903 corresponding to a hit within a given tag block (1986-0 to1986-1) and a given operational cycle. In the very particular embodimentof FIG. 19, a cache data output control 1998 may include data block MUXs1911-0 and 1911-1 and cycle MUX 1911-2. Data block MUX 1911-0 may outputa data value from either group 1909-0 or group 1909-1 in response to hitindications A and B generated by compare section 1996. Similarly, datablock MUX 1911-1 may output a data value from either group 1909-2 orgroup 1909-3 in response to hit indications A and B generated by comparesection 1996. Cycle MUX 1911-2 may output values from data block MUX1911-0 or 1911-1 in response to signals cycle 1 and cycle 2.

In this way, memory devices may include cache architectures withconfigurable associativity.

Referring now to FIG. 20, a cache device according another embodiment isshown in a top plan view, and designated by the general referencecharacter 2046. A cache device 2046 may be one particular example of acache device having an architecture like that shown in FIG. 19.

A memory device 2046 may include cache data memory sections 2015-0 to2015-3, tag blocks 2017-0 to 2017-3, cache controller 2052, busisolation circuits 2064-00 to 2064-13, and data input/outputs (I/Os)2019-0 to 2019-3.

Cache data memory sections 2015-0 to 2015-3 may include storagelocations for data stored in other devices. In one embodiment, datamemory sections 2015-0 to 2015-3 may provide more rapid access to dataalso stored by slower access speed memory devices. Cache data memorysections (2015-0 to 2015-3) may be formed with an architecture having afaster access time than module storage ICs. Cache data memory sections(2015-0 to 2015-3) may include random access memory (RAM) circuits. In aparticular embodiment, cache data memory sections (2015-0 to 2015-3) mayinclude SRAM memory cells, while slower access speed memory devices maybe DRAMs. In another embodiment, cache data memory sections (2015-0 to2015-3) may be SRAMs or DRAMs, and slower speed memory devices may benonvolatile memory ICs, including but not limited to electricallyerasable and programmable read only memories (EEPROMs), such as “flash”EEPROMs.

Tag blocks 2017-0 to 2017-3 may provided data values for compareoperations with address values to determine if a cache hit or cache misshas occurred. That is, in response to an input value (e.g., SET), tagblocks may output a tag value for comparison with an applied tag value.Such compare operations may occur over multiple cycles, as shown in FIG.19.

Cache controller 2052 may include circuitry for controlling functions oncache device 2046 as described for embodiments herein and equivalents.In particular embodiments, cache controller 2052 may form all or aportion of any of: cache controller 1252, 1352, 1452 of FIGS. 12 to 14,and may control operations of cache architecture as described in FIG.19. Data input/outputs (I/O) 2019-0 to 2019-3 may provide read datapaths from and write data paths into cached data memory sections 2015-0to 2015-3.

Bus isolation circuits 2064-00 to 2064-13 may allow signals to flow intoand out of cache device 2046, and in particular embodiments (e.g., lookaside architectures) may allow such signals to flow through cache device2046. In one embodiment, bus isolation circuits 2064-00 and 2064-01 maycarry address and control signals into and/or through memory device2046, while bus isolation circuits 2064-10 to 2064-13 may provide dataI/O paths.

In this way, a cache device may have a centrally located cachecontroller, data I/Os on first opposing ends, and control and addressinputs at second opposing ends.

While embodiments described herein may include standard access speeddevices formed with DRAMs, and faster access devices formed with SRAMs,other embodiments may include may include standard access speed devicesformed with nonvolatile memories (e.g., EEPROMs) and faster accessdevices formed with DRAMs.

Embodiments of the present invention are well suited to performingvarious other steps or variations of the steps recited herein, and in asequence other than that depicted and/or described herein. In oneembodiment, such a process is carried out by processors and otherelectrical and electronic components, e.g., executing computer readableand computer executable instructions comprising code contained in acomputer usable medium.

For purposes of clarity, many of the details of the embodiments ofimpedance programming of the output driver and on-die termination andthe methods of designing and manufacturing the same that are widelyknown and are not relevant to the present invention have been omittedfrom the following description.

It should be appreciated that reference throughout this specification to“one embodiment” or “an embodiment” means that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the invention.

Similarly, it should be appreciated that in the foregoing description ofexemplary embodiments of the invention, various features of theinvention are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureaiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claims require more features than areexpressly recited in each claim. Rather, inventive aspects lie in lessthan all features of a single foregoing disclosed embodiment. Thus, theclaims following the detailed description are hereby expresslyincorporated into this detailed description, with each claim standing onits own as a separate embodiment of this invention.

What is claimed is:
 1. A system, comprising: a plurality of modules,each module comprising a plurality of integrated circuits devicescoupled to a module bus and a channel interface configured tocommunicate with a memory controller, wherein at least one of theplurality of modules is a chunk buffer module comprising: a chunkbuffering section including first type memory cells comprising a firstportion of a total module address space of the chunk buffer module, thefirst type memory cells having a first type of memory interface and afirst maximum access speed, second type memory cells comprising a secondportion of the total module address space of the chunk buffer module,the second type memory cells having a second type of memory interfaceand a second maximum access speed slower than the first access speed,and a memory control section coupled to the module bus and configured togenerate signals compatible with the second type of memory interface inresponse to memory access signals received at the channel interface fromthe memory controller, wherein the chunk buffering section is disposedbetween the channel interface and the memory control section andconfigured to generate signals compatible with the first type of memoryinterface in response to the memory access signals received at thechannel interface from the memory controller.
 2. The system of claim 1,wherein: the second type memory cells comprise dynamic random accessmemory (DRAM) cells; and the first type memory cells comprise staticrandom access memory (SRAM) cells.
 3. The system of claim 1, wherein:the first portion of the total module address space of the chunk bufferis configured to store data with the first type memory cells, and thesecond portion of the total module address space of the chunk buffer isconfigured to store data with the second type memory cells.
 4. Thesystem of claim 1, wherein: the total module address space includes aplurality of data lines of a same size, each data line including aplurality of data bytes, the first portion including N bytes of eachdata line.
 5. The system of claim 1, wherein: at least one module is arapid channel module having a total module address space that storesdata with the first type memory cells and not the second type memorycells.
 6. The system of claim 5, wherein: at least one other module is astandard memory module having storage locations formed with integratedcircuits of the second type memory cells having a first type interfacecoupled to a module interface of the first type by a module bus; and theat least one rapid channel module includes a module interface of thefirst type, and a plurality of integrated circuits of the first typememory cells; wherein the standard module is coupled to a memorycontroller by a first channel, and the rapid channel module is coupledto the memory controller by a second channel.
 7. The system of claim 1,wherein: at least one module is a stacked buffer module having aplurality of integrated circuit (IC) packages, each IC package includinga plurality of memory ICs with second type memory cells, and at leastone cache IC with memory cells of the first type.
 8. The system of claim7, wherein: the at least one cache IC comprises a look-aside cachememory circuit, and a bus isolation circuit having at least a first dataisolation circuit that selectively isolates or connects a moduleinterface to the plurality of memory ICs.
 9. The system of claim 7,further including: the at least one cache memory IC comprises a lookthrough cache memory IC that includes a memory device interface thatgenerates memory control signals for the plurality of memory ICs.